1. Field of the Invention
The present invention relates to a pump for applying cutting fluids to a tool and workpiece in machining operations, and more particularly, relates to a nonrecirculating, solenoid operated pump used in tooling applications.
2. Description of the Prior Art
Heat and chips are carried away from a cutting site where a tool operatively engages a workpiece by a cooling and lubricating fluid which is sprayed or poured onto the workpiece during the machining operation. According to one method, the fluid sprayed onto the cutting site is typically collected in a tank which includes a sump pump. The pump recirculates the fluid, usually an oil, back to the cutting tool through a hose and nozzle. Another common method is to atomize the cutting fluid by producing a mist which is blown at the cutting site. In both cases, cutting fluid is provided on a continuous basis to a large area of the workpiece rather than to just the cutting point during that time during which actual machining occurs. Each method uses a small pump as the essential operative element. Solenoid operated reciprocating pumps are particularly well adapted to intermittent, light duty applications such as this.
Bauer, et al., "Pump", U.S. Pat. No. 3,330,217, shows a rod-like reciprocating pump which uses a rigid reciprocating piston element 130, shown in FIGS. 1 and 3, to pump fluid from an internal chamber into a side port by utilizing the displacing effect of a large, cylindrical piston. A ball check valve is used at the inlet port to restrain the fluid within the pumping chamber as it is displaced from the chamber by the piston into the outlet port.
Solenoid operated pumps utilizing a reciprocating piston are also well-known in the art. Examples are described by Toyoda, et al., "Electromagnetic Pump", U.S. Pat. No. 3,958,902, and "Electromagnetic Plunger Pump", U.S. Pat. No. 4,150,924; and Brooks, "Solenoid Pump", U.S. Pat. No. 2,806,432. However, each of the known prior art references include a system of valving necessitating at least two check valves in order to effectuate a net flow of fluid through the reciprocating pump. Moreover, no means is taught by which oil discharged by the pump can be prevented from siphoning from the discharge nozzle. In addition, each pump is particularly characterized by having a pumping piston within an axial chamber, which piston has a fixed configuration during the power stroke as well as the relaxation stroke. More complex electromagnetic reciprocating pumps have also been devised using independent magnetic coils to actuate the plunger and valving necessary to effectuate a net flow of fluid through the pump.
What is needed is a design for a reciprocating pump which is simplified and reliable and which includes a means for preventing siphoning from the discharge line when the pump is turned off.